Fuzzy Sets and Threatened Species Classification
Helen M. Regan, Mark Colyvan · Conservation Biology · 2000
Fuzzy set theory is a tool with great potential for dealing with uncertainty in conservation biology. In a recent publication in this journal, Todd and Burgman (1998) presented an interesting proposal for incorporating uncertainty and reliability into point-scoring methods of classifying threatened species. In particular, they proposed a fuzzy set-theoretic approach to the method of Millsap et al. (1990). There are, however, problems with this proposal. In the interest of developing such applications of fuzzy set theory in conservation biology, we think it is important to recognize and understand the shortcomings of the proposal advocated by Todd and Burgman (1998) so that such problems might be rectified in future developments. We focus largely on two issues: (1) Todd and Burgman obtain fuzzy membership functions from probabilities, and the argument provided for this strategy is demonstrably fallacious, and (2) given that Todd and Burgman obtain their membership functions from probabilities and advocate fuzzy set-theoretic operations that are analogues of probability operations, the excursion into fuzzy set theory is not necessary.